1. Field of the Invention
The present invention relates to a method of manufacturing a micro electro mechanical system structure, a cantilever-type micro electro mechanical system structure, and a sealed fluidic channel. More particularly, the present invention relates to a method of manufacturing a micro electro mechanical system structure, a cantilever-type micro electro mechanical system structure, and a sealed fluidic channel that eliminates the necessity of using a sacrificial layer provided at a predetermined interval from a substrate.
2. Description of the Related Art
According to a surface micro-machining technology which is based on a semiconductor integrated circuit manufacturing process for machining a thin film element, it is possible to manufacture a minute structure on a silicon substrate and to couple it with semiconductor circuitry, so that a micro electro mechanical system (hereinafter, referred to as “MEMS”) element such as a micro-sensor can be manufactured. Here, in the remaining portion of the minute structure, excepting one side or both sides thereof, it is necessary to form a space so as to float the minute structure over the substrate. Therefore, in order to form the minute structure, a method of using a sacrificial layer has been adopted, and materials which have a good etching selectivity to the structure material have been used as the sacrificial layer.
U.S. Pat. No. 6,762,471 discloses an example of forming a minute structure by using a sacrificial layer as discussed above.
FIG. 1 shows a known minute thin film resonator, which illustrates the construction of the thin film resonator disclosed in U.S. Pat. No. 6,762,471.
In its construction, the thin film resonator 100 is provided with a supporting member (e.g. supporting layer) 155, posts 140 and 141, a first electrode 165, an insulating film 175, and a second electrode 185. The thin film resonator 100 is formed with a predetermined gap (e.g., air gap) on the substrate 110. On the substrate 110, a circuit 105 is present, to which the second electrode 175 and the circuit 105 are connected through a connecting member 220.
FIGS. 2A to 2G illustrate the process used to form the thin film resonator shown in FIG. 1 with a predetermined gap on the substrate, in which a first electrode 165, an insulating film 175, and a second electrode 185 forming a floating structure with a predetermined gap D will be discussed.
Referring to FIG. 2A, the sacrificial layer 120 is deposited on the substrate 110, and then holes 130 and 131 are formed. Next, referring to FIG. 2B, a BPSG (borophosphosilicate glass) layer 135 is deposited. Here, the BPSG layer 135 is embedded through holes 130 and 131 to form posts 140 and 141, which support the thin film resonator 100 that will be formed in the subsequent step. As shown in FIG. 2C, BPSG layer 135, which is deposited on the sacrificial layer 120, is polished. Subsequently, referring to FIG. 2D, in the upper side of the sacrificial layer 120 in which posts 140 and 141 are embedded via holes 130 and 131, a silicon nitride layer 150 is deposited, which becomes a support layer 155. Next, a first metal layer 160 which forms the first electrode 165 is deposited, and a second metal layer 180 which forms the second electrode 185 is deposited. Referring to FIG. 2E, the second metal layer 180, the insulating layer 170, and the first metal layer 160 are patterned sequentially in a shape of the thin film resonator 100. Referring to FIG. 2F, a silicon nitride film 150 is patterned in a shape of the support layer 155, in which openings 195 and 196 are formed. Referring to FIG. 2G, an etching solution containing a hydrofluoric (hereinafter, referred to as “HF”) acid solution moves through the openings 195 and 196 to remove the sacrificial layer 120. Thereafter, washing and drying steps are carried out to form the thin film resonator 100.
The sacrificial layer is generally removed by a wet etching process, i.e., the process of etching after immersing the wafer into a chemical solution containing a HF solution, and then washing and drying.
However, in the above-mentioned conventional method, an undesirable stiction phenomenon occurs, in which the minute structure (e.g., thin film resonator 100) moves down in a space C from which the sacrificial layer is removed due to a capillary force as a result of surface tension during the drying step after washing.
Such stiction phenomenon deteriorates the performance of the minute structure, which leads to a decrease in yield due to failure of the element during manufacturing.